Understanding Smoke Exposure Results: Pinot noir Baseline Concentrations of Smoke Impact Markers across Five Vintages

Abstract

Summary Goals: With increased wildfires in recent years, winemakers must be able to interpret analyses of smoke-related marker compounds to determine whether smoke intrusion has affected their wines. The goal of this study was to examine naturally-occurring, baseline levels of smoke exposure marker compounds in un-oaked Pinot noir to enable winemakers to better understand smoke exposure results. This study also sought to understand how baseline concentrations of smoke marker compounds change from year to year. Key Findings: Pinot noir wines from California and Oregon had detectable baseline levels of free and bound marker compounds, including guaiacol, 4-methylguaiacol, 4-ethylphenol, and m-, p-, and o-cresol. In 2019, the baseline free guaiacol concentration ranged from 1.2 to 2.3 µg/L, while total (free and bound) guaiacol ranged from 6.4 to 12.0 µg/L. The concentration of free guaiacol was greater in older vintages, while total guaiacol did not change much from year to year. The ratio of free to total guaiacol approached 1:2 after five years, suggesting baseline guaiacol may approach an equal ratio of free to bound over time. Impact and Significance: While baseline levels identified here were low, winemakers should become familiar with the baseline concentrations in their wines to better understand risk during smoke-impacted vintages. With increased analysis of non-smoke-impacted, baseline samples, it may be possible to create a variety-specific risk matrix for smoke exposure. Additionally, as wines age, free volatile smoke marker compounds may increase due to normal changes to baseline compounds and may not always represent smoke-related glycosides releasing free volatiles.